Video Transcript
What phenomenon was Moseley
observing and measuring for different elements when he proposed the ordering of
elements could be related to their atomic number? (A) Color, (B) density, (C)
radioactivity, (D) state of matter, (E) X-rays.
Henry Moseley was a British
physicist whose work was important for the creation of the modern periodic
table. Prior to Henry Moseley‘s
experiments, the known elements were organized by atomic weight, as proposed by
Russian chemist Dimitri Mendeleev in 1869. But in 1913, Moseley proposed that
elements should be organized by their atomic number.
At the time, atomic number
represented an element’s position on the periodic table and was equal to the charge
of the nucleus. We now know that the atomic number
is equal to the number of protons in the nucleus of all atoms of an element. Moseley proposed the new ordering
system because he discovered a relationship between the atomic number of an element
and the scattering of X-rays directed at the element.
He recognized from his experiments
that the atomic numbers of elements increased by one unit at a time. His experiments allowed him to
predict the existence of three undiscovered elements and provided a method for
determining whether a substance was in fact a new element.
In conclusion, the phenomenon that
Moseley was observing and measuring when he proposed the ordering of elements could
be related to their atomic number is answer choice (E), X-rays.
